title: Photometry and spectroscopy of the GRB 970508 optical counterpart
abstract: An optical transient within the error box of the gamma ray burst GRB 970508 was imaged 4 hours after the event. It displayed a strong ultraviolet excess, and reached maximum brightness 2 days later. The optical spectra did not show any emission lines, and no variations on time scales of minutes were observed for 1 hour during the decline phase. According to the fireball and afterglow models, the intensity should rise monotonically before the observed optical maximum, but the data indicate that another physical mechanism may be responsible for the constant phase seen during the first hours after the burst.
authors.affiliation: A. J. Castro-Tirado and J. Gorosabel, Laboratorio de Astrofisica Espacial y Fisica Fundamental, INTA, Madrid, Spain. N. Benitez and E. Martinez-Gonzalez, Instituto de Fisica de Cantabria, Santander, Spain. C. Wolf, R. Fockenbrock, K. Birkle, Ma.
authors.forename: A J
authors.initials: AJ
authors.lastname: Castro-Tirado
authors.forename: J
authors.initials: J
authors.lastname: Gorosabel
authors.forename: N
authors.initials: N
authors.lastname: Benitez
authors.forename: C
authors.initials: C
authors.lastname: Wolf
authors.forename: R
authors.initials: R
authors.lastname: Fockenbrock
authors.forename: E
authors.initials: E
authors.lastname: Martinez-Gonzalez
authors.forename: H
authors.initials: H
authors.lastname: Kristen
authors.forename: A
authors.initials: A
authors.lastname: Broeils
authors.forename: H
authors.initials: H
authors.lastname: Pedersen
authors.forename: J
authors.initials: J
authors.lastname: Greiner
authors.forename: E
authors.initials: E
authors.lastname: Costa
authors.forename: M
authors.initials: M
authors.lastname: Feroci
authors.forename: L
authors.initials: L
authors.lastname: Piro
authors.forename: F
authors.initials: F
authors.lastname: Frontera
authors.forename: L
authors.initials: L
authors.lastname: Nicastro
authors.forename: E
authors.initials: E
authors.lastname: Palazzi
authors.forename: C
authors.initials: C
authors.lastname: Bartolini
authors.forename: A
authors.initials: A
authors.lastname: Guarnieri
authors.forename: N
authors.initials: N
authors.lastname: Masetti
authors.forename: A
authors.initials: A
authors.lastname: Piccioni
authors.forename: M
authors.initials: M
authors.lastname: Mignoli
authors.forename: M
authors.initials: M
authors.lastname: Wold
authors.forename: M
authors.initials: M
authors.lastname: Lacy
authors.forename: K
authors.initials: K
authors.lastname: Birkle
authors.forename: T
authors.initials: T
authors.lastname: Broadhurst
authors.forename: S
authors.initials: S
authors.lastname: Brandt
authors.forename: N
authors.initials: N
authors.lastname: Lund